recuremove.rs

use std::ops::DerefMut;
use std::ops::Deref;


#[derive(Show)]
struct List<T> {
    car: T,
    cdr: Option<Box<List<T>>>,
}


fn remove<T: Eq>(node: Option<Box<List<T>>>, value: T) -> Option<Box<List<T>>> {
    match node {
        None => None,
        Some(node) => {
            let mut now = node;
            if now.car == value { now.cdr }
            else {
                now.cdr = remove(now.cdr.take(), value);
                Some(now)
            }
        }
    }
}


fn main() {
    let mut head = Box::new(List {car: 0i8, cdr: None});
    for i in range(1, 42i8) {
        head = Box::new(List {car: i, cdr: Some(head)})
    }
    head = remove(Some(head), 5).unwrap();
    println!("{:?}", head);
}